Date post: | 11-Apr-2017 |
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Karowe Comminution Circuit Upgrade
P. Morgan1, L. van Niekerk1, M. Duddy1 , G. Underwood2 and A. Paz3
1. DRA Global, Johannesburg, No. 3 Inyanga Close, Sunninghill, 2157, South Africa, [email protected], [email protected], [email protected]
2. Minopex, 7 Pinswood Office Park, 33 Riley Rd, Woodmead, 2196, [email protected]
3. Outotec Australia, 40 Kings Park Road, 6005 WA West Perth, Australia, [email protected]
Boteti are due to begin treating the significantly more competent (Unit13) kimberlites at their Karowe Diamond plant, Botswana &
wish to continue with AG milling as the “heart” of their process flow sheet.
Aim: – Assess current performance of the AG mill;
– Assess impact of treating harder kimberlites & increased throughput in the new/modified flowsheet;
– A Turbo-Pulp Lifter (TPLTM) system is anticipated to improve upon the original mill grate/pan lifter operation.
Interpreted Abrasion Factor, ta
Interpreted ta13
FK
S2
S1
y = 2.4x-1
Ap
pare
nt
Dw
i(k
W/m
3)
Observed Relative Grinding Rates
Relative Grinding Rates &DWi Relationship
Relative Hardness(Energy Basis)13
S1
S2
FK
U1
SL
New Circuit Design
• Outotec will provide their innovative
Turbo Pulp Lifter (TPLTM) system to
improve the discharge & grate efficiency;
• Two TPL™ designs will be incorporated:
• 90mm pebble ports for treatment of fragmented kimberlites (FK);
• 115mm pebble ports for hard kimberlites (Unit 13), early 2015.
Turbo-Pulp
Lifter (TPL™)
• DRA used an ‘in-house’ modelling tool to compare
against Outotec’s JKSimMet to assess the proposed circuit;
• Two surveys (S1 & S2) indicated that grate ports were ‘clogging
up’ & pan lifters were ‘retaining material’ that should escape the mill;
• Minerals being processed:
• Unusually hard for a kimberlite;
• Very abrasive, high DMS yields;
• Have high crushing strength;
• Low amenability to scrubbing;
• Large degree of variability (soft
sandstones & weathered kimberlites,
to more competent kimberlites,
mudstones & basalts).
• Using this relationship it was possible to
simulate the mill-crusher circuit
performance when ‘treating’ the
harder ores;
• Initial design trial simulations
indicated that partial pre-crushing,
modified grate design & bypass
screening was necessary to control the
mill overloading;
• Less fines were going to be produced,
potentially overloading the existing DMS circuit;
• High DMS yields are also anticipated on harder ores.
Simulation
Results
Circuit
Benefits
Back-
ground
Weathered
& soft
Bulk
Sample
Milling plant
sampling
audit 2
Milling plant
sampling
audit 1
Fragmented
Kimberlite
Unit 13 Hard
Kimberlite
Deeper material is
more competent
• The fully-
autogenous mill:
offers flexibility for high
variability in the ore;
combines crushing &
scrubbing steps;
• A secondary gyratory crusher will crush a
proportion of jaw crusher product for a consistent
feed to the AG mill;
• Mill discharge screen recycles +60mm directly & combines
with -60mm+32mm LDR tails to the existing pebble crusher;
• Pebble crusher product can be partially split to
bypass mill recycle;
• XRT bulk sorting for Large Diamond
Recovery (LDR);
• -8mm+1.5mm fraction will be
treated in the existing DMS;
• TPL™ for improved
mill capacity &
efficiency.
Benchmarking
showed that the mill
would receive material
significantly harder in the
future (Unit 13) than
seen in the past
(S1 & S2).
Good
Attrition
Good Impact
Slurry
Pool
Poor Impact
Improper
Attrition Turbo
Pulp
Lifter™
Radial
Pulp
Lifter
Sam
ple
Po
pu
lati
on
Dwi(kW/m3)
Karowe Drop Weight Testwork
SMC Karowe Data
PopulationDistributionModel
FK
13
S2
S1
A significant degree of hardness
variation is shown, that prescribes
virtually the complete spectrum
of DWi values.
Published DWidatabase
distribution superimposed
PEBBLE CRUSHER
MILL FEED STOCKPILE
MILL FEED PRE-CRUSHER
EXISTING MILL
+60mm
+1.5x60mm
FINES DMS
JAW CRUSHER
-1.5mm
LARGE DIAMOND RECOVERY
(LDR)
LARGE DIAMOND RECOVERY
(LDR)
CONCENTRATE
PEBBLE BLEED SPLITTER
- 32mm
+32x60mm
+20x32mm
LARGE DIAMOND RECOVERY
(LDR)
MIDDLES BULK
SORTERLARGE DIAMOND
RECOVERY (LDR)
FINES BULK
SORTER
-20mm
+1.5x8mm
TERTIARY CRUSHER and DEWATERING
+8x14mm
+14x32mm
1
7
8
14
15
16
17
12
20
18
+8x60mm
19
42
56
9 10
11
13
ROM FEED
THICKENER FEED
GRITS
TAILS
RECOVERY FEED
CONCENTRATE
Current
Circuit
Constraints
(-8mm)
Legend:
T = Tails
C = Concentrate
T
T
C
C
+32mm
+1.25x8mm
-1.25mm
+1.25x8mm
BLEED
SCREENING
T C